The lack of vegetation together with concomitant low soil OM content usually have an adverse effect on soil microbial biomass and activity. In contrast, the plant community can enhance microbial properties of metal contaminated mine soil (Hernández-Allica et al., 2006). In general, at 0 month, lower or similar values of microbial parameters were found in the NV1 soil than in the NV2 one (p b 0.05): these lower values may reflect significant higher values of CaCl2-extractable Pb in the NV1 soil (Table 1). Vegetated soils (V1 and V2) had higher CaCl2-extractable Zn values than non-vegetated soils (NV1 and NV2): in vegetated soils, Zn was probably sorbed to roots (Table 1), while, in non-vegetated soils, labile Zn might have been lost through leaching. The beneficial effect of vegetation on soil microbial communities more than counteracts the potential negative effect of higher bioavailable Zn concentrations. By contrast, at 0 month, soil phytotoxicity, as reflected by L. sativa root elongation, was in many cases not significantly different in vegetated versus non-vegetated sites (Fig. 3).